Wind turbine blade having twisted spar web

ABSTRACT

A radially twisted wind turbine blade ( 10 ), including a radially twisted spar web ( 122 ), wherein a center ( 78 ) of a radial cross section of a base ( 12 ) of the blade rotates within a plane of rotation ( 80 ), and wherein at a base ( 12 ), a radial cross section of the spar web forms a first angle ( 82 ) with the plane of rotation, and at a tip ( 32 ) a radial cross section of the spar web forms a second angle ( 130 ) with the plane of rotation different than the first angle.

FIELD OF THE INVENTION

The present invention relates to wind turbine blades. In particular, the present invention relates to a wind turbine blade that allows for an increased resistance to flap deflection without adding weight or increasing torsional rigidity.

BACKGROUND OF THE INVENTION

Wind turbines include wind turbine blades that are secured to a rotor hub. The blades and rotor rotate about an axis of rotation and drive a rotor shaft. The rotor shaft, in turn, drives a generator arrangement disposed in a nacelle located adjacent to the rotor hub. The generator arrangement and nacelle are disposed atop a support tower.

At a base of the blade a linear velocity for any given radial location is determined by the formula V_(linear)=rω, where r is a radius and w is a rotational velocity. Thus, at the base, where the radius is shorter, the V_(linear) is less than at the tip of the blade. Assuming the blade is rotation in when there is no wind, the linear velocity of the blade causes the blade to move through the air, and this creates a “rotational relative wind” across the blade that the blade sees as wind moving at the same speed as the linear velocity of the blade for any given point. For purposes of discussion, each radial location of the blade will be referred to as a radial point, and the radial point refers to a center of a cross section of the blade at the radial location. During rotation each point on the blade rotates within a plane of rotation. Consequently, for any given point the rotational relative wind appears to be wind with a vector parallel to the plane of rotation, and the speed of the rotational relative wind increases toward the tip of the blade.

During normal operation, the wind turbine operates within environmental wind that with an environmental wind vector. The environmental wind vector may be parallel to the axis of rotation of the wind turbine, making it perpendicular to a plane of rotation for any point on the blade. Consequently, each point of the blade encounters environmental wind and rotational relative wind. Thus, each point of the blade encounters what is known as a relative wind, which is a sum of the vectors of the environmental wind and the rotational relative wind. An environmental wind vector may be the same at the base and at the tip of the blade, and it may be perpendicular to the plane of rotation. However, a vector of the rotational relative wind increases in magnitude from the base to the tip of the blade, while the direction is parallel to the plane of rotation. As a result, the relative wind vector for each point changes from being closer to perpendicular to the plane of rotation at the base of the blade to being closer to parallel to the plane of rotation at the tip of the blade. In current technology blades the change in orientation may be up to 30 degrees, depending on the blade design. Changes in orientation up to 45 degrees are currently envisioned. The twisted web disclosed herein can accommodate any amount of change in orientation.

Wind turbine blades use forces created by the relative wind to drive the rotation of the blade about the rotor hub. As the relative wind reaches the blade some of it encounters a pressure side of the blade to create a pressure side aerodynamic force that can be seen as acting normal to the pressure side of the blade. Some of the relative wind is directed around the blade along a suction side. This suction side relative wind travels faster than the pressure side relative wind, and this velocity difference creates a suction side aerodynamic force that can be seen as acting normal to the suction side of the blade. The pressure side aerodynamic force and the suction side aerodynamic force each have a force component parallel to the plane of rotation (a rotational component) and a force component perpendicular to the plane of rotation. These forces sum up to a net aerodynamic force acting on each point of the blade, where the net aerodynamic force changes orientation from almost parallel to the plane of rotation of a point at the base to almost perpendicular to a plane of rotation of a point at the tip. The net aerodynamic force then has a component parallel to the plane of rotation, (a rotational component), and a component perpendicular to the plane of rotation. In order to ensure the relative wind, which changes orientation from the base to the tip, travels over the pressure side and suction side in manner best suited to maximize a rotational component of the net aerodynamic force, the blade itself also changes orientation with the relative wind, from base to tip. This results in a “twisted” blade configuration, where at the base the blade is oriented nearly parallel to the environmental wind, and where at the tip the blade may be oriented nearly perpendicular to the environmental wind.

Wind turbine blades are not perfectly rigid. As a result, the net aerodynamic forces acting on each point of the blade cause the blade to deflect. This deflection, known as flap deflection, may be parallel to a direction of the net aerodynamic force. The net aerodynamic force may be perpendicular to the relative wind. Thus, at the base a point may experience a deflection force close to parallel to the plane of rotation, while toward the tip a point may experience a deflection force close to perpendicular to the plane of rotation. Deflection parallel to the plane of rotation is of mild concern. However, deflection perpendicular to the plane of rotation is of great concern because the support tower is located not too far from the blades. Too much deflection of the blade toward the support tower and the blade may collide with the support tower.

In order to reduce flap deflection, certain blade designs incorporate a structural spar. The spas is shaped similar to an I-bean, and may have a pressure side spar cap, a suction side spar cap, and a spar web securing and holding the spar caps in a spaced apart relationship. The spar adds strength and rigidity, but also adds weight to the blade. In conventional blade designs, a spar is installed in a blade from base to tip, and at all locations from the base to the tip the spar web maintains a same angle with the plane of rotation. In other words, the spar is a planar member. However, as blades grow in length, weight and stiffness are of growing concern. Consequently, there remains room in the art for improvement.

SUMMARY OF THE INVENTION

A wind turbine blade having a unique structural spar is disclosed. The structural spar has a spar web that twists within the blade, from a base of the blade to a tip of the blade. By allowing the spar web to deviate from planar, an orientation of the web can be selected as an independent design variable for the first time. For any given radial location the orientation of the spar web may be selected in a manner that best resists deflection of the blade induced by aerodynamic forces acting at that given location. At the base of the blade rotational forces (within the plane of rotation) are greatest, and deflection forces (toward the tower, perpendicular to the plane of rotation) are weakest. Consequently, at the base of the blade the spar can be oriented nearly parallel to the direction of rotation to resist rotational forces, and at the tip of the blade it can be oriented nearly perpendicular to the plane of rotation to resist tower deflection.

Furthermore, because blade stiffness has become a primary design concern, and because prior art spar webs could not tailor the spar web strength to resist tower deflection, prior art spar webs were built to standards much higher than blade strength alone (as opposed to stiffness) required. Consequently, because the strength of the spar web can be specifically tailored to resist local deflection forces, for a given stiffness requirement of a given blade, the structural spar may be made lighter. The lighter structural spar may have lighter spar caps. Lighter spar caps allows for increased torsional flexibility which decouples the tower stiffness from a twist stiffness. Therefore, for the given blade, the present invention would allow for a comparable stiff blade that would have a lighter spar, and reduced torsional rigidity. The reduced torsional rigidity would allow the blade to torsionally flex (twist) in relatively strong winds. Such a characteristic is desirable as it allows the blade to become aeroelastic. The twist of an aeroelastic blade during high winds allows it to decrease an angle of attack of the blade with respect to the relative wind, and this reduces transient stresses on the blade.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in the following description in view of the drawings that show:

FIG. 1 is a perspective view of a schematic representation of a turbine blade.

FIG. 2 is a side view of the turbine blade of FIG. 1.

FIG. 3 is a radial cross section of a prior art blade showing a spar web.

FIG. 4 is a radial cross section of the prior art spar blade of FIG. 3 taken at a cross-section closer to the blade tip that the cross section of FIG. 3.

FIG. 5 is a radial cross section of an exemplary embodiment of the spar web disclosed herein, taken along line A-A of the blade of FIG. 1.

FIG. 6 is a radial cross section of an exemplary embodiment of the spar web disclosed herein, taken along line B-B of the blade of FIG. 1.

FIG. 7 is a radial cross section of an alternate exemplary embodiment of the spar web disclosed herein, taken along line A-A of the blade of FIG. 1.

FIG. 8 is a radial cross section of an alternate exemplary embodiment of the spar web disclosed herein, taken along line B-B of the blade of FIG. 1.

FIG. 9 is a radial cross section of another alternate exemplary embodiment of the spar web disclosed herein, taken along line B-B of the blade of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The present inventor has recognized that blade design has evolved from designing blades of sufficient strength to designing blades of stiffness sufficient to prevent the blade from colliding with the tower support. The present inventor has also recognized that local forces change from a base of the blade to a tip of the blade. In particular, at the base of the blade rotational forces (within a plane of rotation) have “accumulated” from the tip to the blade to the base, while tower deflection forces (toward the tower) are negligible. A skin of the blade is very robust at the blade and can withstand the deflection forces itself, but may need the assistance of a structural spar to handle the rotational forces. In contrast, at the tip of the blade the rotational forces are negligible, while deflection forces have “accumulated” from the base to the tip, resulting in greater tower deflection. Since the blade is thin and oriented close to parallel to the plane of rotation, it can handle the rotational forces itself, but may need the assistance of the structural spar to prevent too much tower deflection.

Blade rigidity comes primarily from the structural spar incorporated into the blade. The present inventor has devised a unique way to orient the spar by twisting it in a radial direction so that it may be aligned with local forces that would induce deflection. Specifically, at the base the web would be oriented nearly parallel to the plane of rotation in order to resist rotational forces, and at the tip it would be oriented nearly perpendicular to the plane of rotation to resist tower deflection. This allows for a structural spar of reduced strength and weight, because a greater percentage of its existing strength is being used in each radial location. However, since structural spars have evolved to be stronger than needed, (as opposed to stiffer), the proposed structural spar of reduced strength and weight will be sufficient. The reduced strength and weight allow for greater torsional flexibility (twisting), and thus the blade may have superior aeroelastic properties, including aeroelastic deformation (twist) during high wind loading.

FIG. 1 discloses a blade 10 of a wind turbine. A base 12 of the blade 10 is secured to a rotor hub 14. The rotor hub 14 is secured to a rotor shaft 16 that leads to a power generation system (not shown) disposed inside a nacelle 18, that sits atop a support tower (not shown). A leading edge 30 (indicated by a dotted line) of the blade 10 spans from the base 12 to a tip 32. It can be seen that the blade twists such that at the base 12 the leading edge 30 is oriented almost directly into environmental wind traveling in an environmental wind vector 34. Toward the tip 32 the leading edge 30 turns such that it is pointed nearly perpendicular to the environmental wind vector 34. As seen from the rotor hub 14, the twist rotates in a clockwise direction 36. As seen from a position 37 upwind with respect to the environmental wind vector 34, the blade 10 rotates in a clockwise direction of blade rotation 38 about an axis of rotation 40. Any given point on the blade 10 therefore defines a respective plane of rotation (not shown). The blade has a pressure side 42 and a suction side 44.

FIG. 2 shows a side view of the blade 10 of FIG. 1. The blade 10 rotates in a direction of blade rotation 38 shown as an arrow head. In this view the direction of blade rotation 38 is out of the page. For sake of simplicity, a cross section of each radial location will be modeled as a point in a center of a respective cross section throughout this disclosure. During rotation each radial point moves in a respective plane of rotation. If the blade 10 rotates and no aerodynamic forces are generated, each point rotates about a respective no-load plane of rotation. When there is environmental wind, however, the blade deflects due to aerodynamic loads. The deflection of any given point may be in any direction. However, a tower deflection 50 of the tip 32 from a no-load plane of rotation 52 to a load plane of deflection 54, which is closer to the support tower 56, is of direct concern. The twisted spar web disclosed herein directly addresses this tower deflection 50.

FIG. 3 is a cross section of a prior art turbine blade similar to that of FIG. 1 taken near the base the blade looking radially outward from the rotor hub (not shown) showing a prior art structural spar 70 having a spar web 72, a pressure side spar cap 74 disposed in the pressure side 44, and a suction side spar cap 76 disposed in the suction side 46. The leading edge 30 of the blade is oriented almost directly into the environmental wind vector 34. The base is moving in the direction of blade rotation. Each cross section has a center 78 that rotates within a respective plane of rotation 80. The spar web 72 forms a first angle 82 with the plane of rotation 80.

During rotation the cross section center 78 experiences the influences of the environmental wind vector 34 and a rotational relative wind vector 90 that is parallel to the respective plane of rotation 80. These vectors combine to form an effective wind for the given center 78 known as the relative wind having a relative wind vector 92. The relative wind vector 92 is simply the sum of the environmental wind vector 34 and the rotational relative wind vector 90. As the relative wind passes over the pressure side 44 it creates a pressure side aerodynamic force vector 100 that can be said to act on the center 78 essentially normal to the pressure side 44. As the relative wind passes over the suction side 46 it creates a suction side aerodynamic force vector 102 that can be said to act on the center 78 essentially normal to the suction side 46. The pressure side aerodynamic force vector 100 and the suction side aerodynamic force vector 102 may or may not be parallel to each other. A net aerodynamic force vector 106 acting on the center 78 is a sum of the pressure side aerodynamic force vector 100 and the suction side aerodynamic force vector 102. The net aerodynamic force vector 106 forms a net force angle 108 with the plane of rotation 80, and therefore the net aerodynamic force vector 106 has a net aerodynamic force tower component 110 perpendicular to the plane of rotation 80, which is toward the support tower (not shown), and a net aerodynamic force in-plane component 112 that is parallel to the plane of rotation 80. It can be seen that the net aerodynamic force in-plane component 112 is much greater than the net aerodynamic force tower component 110 at the base 12. A shell 114 of the base 12 is also more substantial structurally. Consequently, at the base 12 the resistance to the net aerodynamic force in-plane component 112 is of high importance, while tower deflection 50 is of little concern.

FIG. 4 is a cross section close to the tip of the blade of FIG. 3 looking radially outward from the rotor hub (not shown) showing a prior art structural spar 70 having a spar web 72, a pressure side spar cap 74 disposed in the pressure side 44, and a suction side spar cap 76 disposed in the suction side 46. In contrast to the base, the leading edge 30 of the blade 10 at the tip is oriented closer to perpendicular to the environmental wind vector 34. The tip 32 is moving in the direction of blade rotation 38. Each cross section has a center 78 that rotates within a respective plane of rotation 80. The spar web 72 again forms the same first angle 82 with the plane of rotation 80. This occurs because the spar web 72 is planar.

Similar to the base 12, during rotation the cross section center 78 of the tip 32 experiences the influences of the environmental wind vector 34 and a rotational relative wind vector 90 that is parallel to the respective plane of rotation 80. These vectors combine to form the relative wind vector 92. The relative wind creates the pressure side aerodynamic force vector 100 and the suction side aerodynamic force vector 102. The net aerodynamic force vector 106 acts on the center 78. The net aerodynamic force vector 106 forms the net force angle 108 with the plane of rotation 80, and therefore the net aerodynamic force vector 106 has the net aerodynamic force tower component 110 and the net aerodynamic force in-plane component 112. It can be seen that the net aerodynamic force tower component 110 is much greater than the net aerodynamic force in-plane component 112 at the tip 32. Consequently, at the tip 32 the resistance to the tower deflection 50 is of high importance, while resistance to the net aerodynamic force in-plane component 112 is of little concern. This is the opposite of what happens at the base 12. However, in the prior art an orientation of the spar web 72 is not tailored to accommodate the differing requirements of the base 12 and the tip 32. Whatever orientation selected was a compromise, and any shortcomings were corrected by building the spar web bigger, stronger, and heavier.

In contrast, FIGS. 5-9 show an exemplary embodiment of the spar web disclosed herein that is tailored to provide strength as required by particular regions throughout the blade 10. FIG. 5 is the same cross section as FIG. 3, but with a spar 120 disclosed herein, having a spar web 122, a pressure side spar cap 124 on the pressure side, and a suction side spar cap 126 on the suction side 46. As in the prior art, the net aerodynamic force vector 106 acts on the center 78. Unlike the prior art, the spar web 122 is parallel to the plane of rotation 80, and thus the first angle 82 is zero and the spar web 122 will offer maximum resistance to in-plane forces. The spar web 122 as shown does not exactly align with the net aerodynamic force vector 106. Consequently, for the given net aerodynamic force vector 106 the spar web 122 may offer little resistance to tower deflection 50. However, since tower deflection 50 is such a small concern at the base 12, and since in-plane resistance is so important, this configuration may be a good match of the spar web's strength to the needs of the base 12 of the blade 10. The first angle may be less than 45 degrees to most effectively resist deflection in the plane of rotation 80.

FIG. 6 is the same cross section as FIG. 4, with the spar 120 disclosed herein. Similar to the prior art, there is the net aerodynamic force vector 106 that acts on the center 78. However, unlike the prior art, the spar web 122 at the tip 32 forms a second angle 130 with the plane of rotation 80, where the second angle 130 is different than the first angle 82 at the base 12. In the exemplary embodiment shown the spar web 122 at the tip 32 does not exactly align with the net aerodynamic force vector 106 at the tip 32, but it is exactly perpendicular to the plane of rotation 80. Instead, the spar web 122 forms an alignment angle 132 with the net aerodynamic force vector 106 which may be within 45 degrees of the net aerodynamic force vector 106. Consequently, for such an exemplary embodiment and for the given net aerodynamic force vector 106, the spar web 122 may offer little resistance to in-plane force, but it will offer maximum resistance to tower deflection 50. Since tower deflection 50 is so importance at the tip 32, and in-plane resistance is such a small concern at the tip 32, this configuration may be a good match of the spar web's strength to the needs of the top 32 of the blade. The second angle 130 may be greater than 45 degrees to most effectively resist deflection in the plane of rotation 80.

Alternately, as shown in FIG. 7, the spar web 122 at the base 12 may exactly align with the net aerodynamic force vector 106. This may provide maximum resistance to the net aerodynamic force vector 106, but may offer slightly less in-plane resistance. Similarly, as shown in FIG. 8, the spar web 122 at the tip 32 may exactly align with the net aerodynamic force vector 106, such that the alignment angle 132 between the spar web 122 and the net aerodynamic force vector 106 is zero. This provides a maximum resistance to deflection induced by the net aerodynamic force vector 106 that has been designed for at that location. However, it may permit minimal tower deflection 50 should force vectors change.

With the spar web 122 disclosed herein, a greater portion of the spar web's strength will still be applied locally as needed. This allows rigidity to be treated as in independent design factor, which has not previously occurred.

Further, the first angle 82 and/or the second angle 130 may be selected as a result of considering factors other than the local net aerodynamic force vector 106. In other words, a net bending force/moment on any given cross section may be considered to be the local net aerodynamic force vector 106 alone, or it may be considered to include the local net aerodynamic force vector 106 and other forces, such as forces induced by non local parts of the blade, or any other force known to those of ordinary skill in the art. In addition, a local geometry of the blade cross section may require or suggest adjustments. For example, as shown in FIG. 9, the spar web 122 has been shifted closer to the leading edge 30. As a result of this shift, and the local blade geometry, an average length 140 of the spar web 122 between the pressure side spar cap 74 and the suction side spar cap 76 may be longer than if the spar web 122 were positioned as in FIG. 8, over the center 78. (The average length as used herein accounts for angled ends of the spar web 122 due to the angled spar caps.) In certain instances, an additional amount of strength gained by lengthening the spar web 122 may make up for a slight misalignment with whichever direction the spar web's 122 strength is needed. Alternately, or in addition, the spar web 122 can be rotated so that it does not exactly align with the net aerodynamic force vector 106, or with whichever direction the spar web's 122 strength is needed, for the same reason. For example, a different second angle 130 may be used than the second angle 130 of FIG. 8. Other forces may be considered not discussed herein but known to those of ordinary skill in the art. Each cross section may be looked at and an orientation of the spar web 122 may be optimized for each cross section when all factors are considered.

One way to optimize the average length 140 of the spar web 122 may be to determine a tangent line 150 of the leading edge 30, and then draw a pressure side line 152 perpendicular (i.e. at a right angle) to the tangent line 150 and determine a pressure side tangent point 154 where the pressure side line 152 contacts the pressure side 44. Then drawing a suction side line 156 perpendicular to the tangent line 150 and determine a suction side tangent point 158 where the suction side line 156 contacts the suction side 46. A suggested spar web line 160 connecting the pressure side tangent point 154 and the suction side tangent point 158 may reveal a spar web orientation that yields a greatest average length 140 of the spar web for that local blade geometry, and the greatest average length 40 may provide a desired design choice.

A resulting spar web 122 may twist at a smooth, constant rate from base to tip, (i.e. curvilinear), or it may twist in a smooth, but not necessarily constant rate. As used herein, smooth means not abrupt changes in twist direction, such as may occur if a spar web were cut into a radially inner piece and a radially outer piece, and one piece were rotated any amount, and then the two were rejoined.

From the foregoing is can be seen that the inventor has devised an innovative way to decouple the blades rigidity requirement, the strength requirement, and the torsional rigidity requirement from each other, by using a structural spar that can be twisted to accommodate local forces. Since the blade depends on the spar for to supply structural strength in different directions for different reasons at differing location, the twisted spar can be tailored to provide much more of its available strength exactly as needed for any given location within the blade. This permits a lighter spar for a given rigidity requirement, and this lighter spar still meets the blade's strength requirement, while permitting greater torsional flexibility. The greater torsional flexibility enables a more aeroelastic blade, and a more aeroelastic blade may have a longer service life. Consequently, this spar represents an improvement in the art.

While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims. 

The invention claimed is:
 1. A radially twisted wind turbine blade, comprising a radially twisted spar web, wherein a center of a radial cross section of a base of the blade rotates within a plane of rotation, and wherein at a base, a radial cross section of the spar web forms a first angle with the plane of rotation, and at a tip a radial cross section of the spar web forms a second angle with the plane of rotation different than the first angle.
 2. The wind turbine blade of claim 1, wherein the first angle is less than the second angle.
 3. The wind turbine blade of claim 2, wherein the first angle is less than 45 degrees, and the second angle is greater than 45 degrees.
 4. The wind turbine blade of claim 1, wherein a twist of the spar web is curvilinear from a base of the spar web to a tip of the spar web.
 5. The wind turbine blade of claim 1, wherein from a base of the spar web to a tip of the spar web the spar web is located between a pressure side spar cap and a suction side spar cap to maximize an average length of the spar web between the pressure side spar cap and the suction side spar cap.
 6. The wind turbine blade of claim 1, wherein a tangent of a leading edge of the blade forms right angles with a tangent line of a pressure side of the blade and a tangent line of a suction side of the blade, and the spar web spans between a tangent point of the pressure side tangent line and a tangent point of the suction side tangent line.
 7. The wind turbine blade of claim 1, further comprising spar caps secured to ends of the spar web, wherein the spar web and the spar caps are configured to enable aeroelastic deflection during high wind loading.
 8. A radially twisted wind turbine blade, comprising a radially twisted spar web configured to hold a pressure side spar cap and a suction side spar cap in a spaced-apart relationship, wherein a center of a radial cross section of a base of the blade rotates within a plane of rotation, wherein a base, the spar web is oriented such that it resists deflection of the spar web in a direction parallel to the plane of rotation more than it resists deflection of the spar web in a direction perpendicular to the plane of rotation; and wherein at a tip the spar web is oriented such that it resists deflection of the spar web in the direction normal to the the plane of rotation more than it resists deflection of the spar web in the direction parallel to the plane of rotation.
 9. The wind turbine blade of claim 8, wherein the spar web further enables aeroelastic deflection during high wind loading.
 10. The wind turbine blade of claim 8, wherein from a base of the spar web to a tip of the spar web the spar web is located between the pressure side spar cap and the suction side spar cap to maximize an average length of the spar web between the pressure side spar cap and the suction side spar cap.
 11. The wind turbine blade of claim 8, further comprising spar caps secured to ends of the spar web, wherein the spar web and the spar caps are configured to enable aeroelastic deflection during high wind loading.
 12. The wind turbine blade of claim 8, wherein a twist of the spar web comprises no abrupt changes.
 13. The wind turbine blade of claim 8, wherein a tangent of a leading edge of the blade forms right angles with a tangent line of a pressure side and a tangent line of a suction side, and the spar web spans between a tangent point of the pressure side tangent line and a tangent point of the suction side tangent line.
 14. A radially twisted wind turbine blade, comprising a radially twisted spar web, wherein the turbine blade twists from a base of the blade to a tip of the blade, wherein a center of a radial cross section of the base of the blade rotates within a plane of rotation, and wherein within each radial cross section of the blade the spar web forms an alignment angle of less than 45 degrees with a direction of a net bending moment.
 15. The wind turbine blade of claim 14, wherein the alignment angle is zero within at least one radial cross section.
 16. The wind turbine blade of claim 14, wherein for an orientation of the respective spar web in each cross section, the respective spar web is located to maximize an average length of the spar web.
 17. The wind turbine blade of claim 14, further comprising spar caps secured to ends of the spar web, wherein the spar web and the spar caps are configured to enable aeroelastic deflection during high wind loading.
 18. The wind turbine blade of claim 14, wherein a twist of the spar web is curvilinear from the spar web base to the spar web tip.
 19. The wind turbine blade of claim 14, wherein a tangent of a leading edge of the blade forms right angles with a tangent line of a pressure side and a tangent line of a suction side, and the spar web spans between a tangent point of the pressure side tangent line and a tangent point of the suction side tangent line. 